Infrared cameras detect infrared radiation emitted by the objects of a scene, and generate an image of the scene from the detected radiation. An infrared camera has a temperature detector that detects subtle temperature changes in the scene such as changes of less than one degree Fahrenheit. The detector may also be extremely sensitive to camera temperature changes that cause unintentional signal offsets.
The signal offsets may be subtracted from the signal. Typically, subtraction may be performed by factory calibration followed by real-time calibration. According to known techniques for real-time calibration, the detector may be blocked by a shutter in order to provide a constant reference from which samples may be collected. The samples may then be used to determine a signal offset. Dropping the shutter during collection, however, does not allow the detector to gain information about the scene.